Why the thin black curtain on the window?
Thoughts:
1. To block some sunlight from getting in.
2. It’s a secure facility and wanted to prevent people from looking in.
3. To not have to look at something outside.
4. It’s a secure facility and wanted to prevent the chance of taking a picture of someone or something outside that could compromise the location of the computer or someone’s identity; sometimes the first place a photogenic computer was built was at a customer site.
Many computer rooms had windows. Computers were expensive things that companies often wanted to show off - but they needed special rooms with raised floors, HVAC (which also make them look even more exclusive/impressive and worth showing off), and the cost (millions of dollars when senior operators might be making $50k/year) meant you wanted to be careful who could touch them. Thus a window so that you could bring outsiders by the room on the way to a meeting and they could look in and see that shiny equipment.
Remember in 1980 the modern PC wasn't even invented (Apple II was) yes. Most people didn't have access to any terminal as part of their job, only specialized positions did. Typewriters where was everyone had on their desk. As such a computer was something a company could wow visitors with. Times have changed.
It was the 70s, and that was simply the style at the time.
I suspect the curtains are closed to avoid causing exposure issues etc. in the photos being taken.
As for windows in a computer room, seems a bit unusual, but a nicer working environment than the usual windowless box I'd guess...